U.S. Pat. No. 5,164,734 of Duane G. Fredericks et al. disclosed and claimed an apparatus for producing an electromagnetic signal which contained: (a) means for receiving a radar signal which has frequency of from about 10 to about 94 gigacycles, (b) means for decreasing the frequency of said radar signal by at least about 65 percent, thereby producing a reduced frequency electromagnetic signal with a center frequency of from about 700 to about 1,300 megacycles; (c) delay means for delaying said reduced frequency electromagnetic signal by at least about three radar pulse widths and from about 5 to about 100 microseconds, thereby producing a delayed electromagnetic signal wherein the delay means is comprised of a first delay circuit and a second delay circuit, each of which is substantially non-attenuating and non-dispersive, (d) means for increasing the frequency of said delayed electromagnetic signal to produce a delayed electromagnetic wave with an increased frequency which is substantially identical to the frequency of said radar signal, thereby producing a delayed radar signal of from about 1 to about 94 gigagcycles; (e) means for modulating said delayed radar signal with a frequency of from about 1 to about 94 gigacycles, thereby producing a modulated, delayed radar signal; and (f) means for transmitting said modulated, delayed radar signal. The entire disclosure of this United States patent is hereby incorporated by reference into this specification.
However, the device claimed in U.S. Pat. No. 5,164,732 was operable only over a relatively narrow bandwidth and, because it utilized down conversion, produced spurious emissions.
It is an object of this invention to produce a radar target with delayed reply means that overcomes these limitations.
It is another object of this invention to provide a process evaluating the radiation pattern of a phased array antenna using the radar target of this invention.
In accordance with this invention, there is a process for evaluating the radar pattern of a phased array antenna utilizing transmissions from a global positioning satellite, comprising the steps: (a) providing a delayed radar target on a moving platform, a remote differential global positioning receiver on said moving platform, a fixed global positioning receiver on said phased array antenna, and a data link between said remote differential global positioning receiver and said fixed global positioning receiver, (b) radiating a first signal from said radar towards a said delayed radar target, (c) receiving a first radar reply from said delayed radar target, (d) receiving a second signal from said global positioning satellite at said remote global positioning receiver from said global positioning satellite, (e) receiving a third signal at said fixed global positioning receiver from said remote global positioning receiver, and (f) transmitting a fourth signal from said global positioning satellite to said fixed global positioning receiver, and (g) processing said first signal, said second signal, said third signal, and said fourth signal.